In the past, coaxial cables have been widely used as various electric wires and cables: such as a signal transmission cable for an industrial robot or medical equipment such as an endoscope and a diagnostic probe of ultrasonic diagnostic equipment; and a cable for internal connection of information equipment such as a notebook-sized personal computer, and a portable device such as a mobile phone or a PDA. FIG. 1 is a perspective view schematically showing a structure of a coaxial cable. The coaxial cable 10 has a core conductor 11, an insulator 12 arranged at the outer periphery of the core conductor 11, and an outer conductor 13 arranged, at the outer periphery of the insulator 12, coaxially with respect to the core conductor 11, and generally a jacket 14 made of resin, etc. is provided around the outer periphery of the outer conductor 13. In many cases, the coaxial cable used in such an electric equipment as mentioned above is repeatedly subjected to bending in addition to tensile stress during use, which results in accumulation of strain, and in a worst case, a cable may be damaged or broken. Therefore, a coaxial cable widely used has a core conductor 11 made in a stranded wire structure in which a plurality of copper or dilute copper alloy wires 11a are stranded together in order to enhance bending resistance. In a patent document 1, in order to improve bending resistance, it is proposed to make a core conductor in a stranded wire structure in which conductor wires are stranded together such that the elastic modulus of a central wire is larger than the elastic modulus of wires in an outer layer. On the other hand, a patent document 2 proposes that a core conductor be made of single solid wire having a specific composition, instead of stranded wires, lest an accident such as short circuit occur due to loosening of the stranded wires.
Patent document 1: Japanese Patent No. 3376672
Patent document 2: Japanese Patent Application Publication No. 2001-23456